The newly added languages are commonly spoken in at least 60,000 households in which English language skills were lacking, according to data from the census' 2016 American Community Survey.

The US Census Bureau now offers glossaries and other information in a total of 59 languages, including Lithuanian, Somali and American Sign Language -- all of them spoken most commonly in more than 2,000 households.

The paper census forms are available only in Spanish and English.

The Census Bureau tracks data on minority groups it deems "hard to count" and publishes an interactive map showing the exact locales where low numbers of households have mailed back census questionnaires.

The newly available languages come at the recommendation of the Census Bureau's National Advisory Committee on Racial, Ethnic, and Other Populations. By allowing these Americans to fill out forms online in languages with which they're most comfortable, the bureau is betting they'll get a more accurate count.

Groups such as Arab-Americans have been hard to count

Maya Berry, executive director for the Arab American Institute, told CNN that adding the new languages, including Arabic, was "wonderful news."

She cited Census data that there are 1.2 million Arabic speakers in the United States -- not just among immigrants but native residents, as well. Arab-American groups have been advocating for years to have census questions in Arabic.

Arab-Americans have been a historically undercounted group, says Berry, who believes online questionnaires in Arabic will encourage more Arab residents to participate.

But Berry says she is disappointed the census won't include a question asking about Middle East and North African (MENA) ethnicity. Currently, Arab-Americans don't have an ethnic box they can check on the census form, and many have to categorize themselves as "white" or "other."

In January 2018 the Census Bureau announced it would not add the so-called "MENA" question. In a public meeting about 2020 census preparations, Karen Battle, who heads the bureau's population division, said the bureau needed to do more testing on MENA "as an ethnicity, separate from the race question."

Berry says the Middle East and North Africa category covers a geographical swath that also includes people who consider themselves black or brown. In addition to immigrants from the 22 Arab League nations, it would count people who'd come to America from other countries, such as Iran.